Method of increasing molecular weight of polymer

ABSTRACT

1. THE PROCESS OF INCREASING THE MOLECULAR WEIGHT OF A POLYMER OF THE CLASS CONSISTING OF TERMINALLY LITHIATED HOMOPOLYMERS OF CONJUGATED DIENES CONTAINING 4 TO 6 CARBON ATOMS AND TERMINALLY LITHIATED COPOLYMERS OF SUCH CONJUGATED DIENES AND A VINYL MONOMER, WHICH COMPRISES JOINING THE UNITS OF THE POLYMER WITH SUBSTANTIALLY EQUIMOLAR AMOUNTS OF TUNGSTEN HEXACHLORIDE AND TRIISOBUTYLALUMINUM WHICH CAUSES JOINING THE POLYMER AND PRODUCTION OF A POLYMER OF INCREASED MOLECULAR WEIGHT.

United States Patent 3,845,028 METHOD OF INCREASING MOLECULAR WEIGHT 0F POLYMER Tristram Walker Bethea and Adel Farhan Halasa, Akron, Ohio No Drawing. Continuation of application Ser. No. 82,157, Oct. 19, 1970, which is a continuation of application Ser. No. 776,817, Nov. 18, 1968, both now abandoned.

This application Dec. 4, 1972, Ser. No. 312,207

Int. Cl. C08d 5/02, 5/04 U.S. Cl. 26085.1 1 Claim ABSTRACT OF THE DISCLOSURE The molecular weight of a lithiated unsaturated polymer is increased by treatment with a salt of a transition metal, preferably also with an organometallic compound.

This is a continuation of application Ser. No. 82,157 (now abandoned), filed Oct. 19, 1970, which in turn is a streamline continuation of application Ser. No. 776,817 (now abandoned), filed Nov. 18, l968.

This invention relates to increasing the molecular weight of a polymer by joining lithiated polymers of a lower molecular weight. The polymers capable of being joined are lithiated homopolymers of a conjugated diene containing 4 to 6 carbon atoms or lithiated copolymers of such conjugated dienes or lithiated copolymers of such a conjugated diene and a vinyl monomer. The products are not lithiated; they are rubbery.

To increase the molecular weight, the polymer is treated with a salt of a transition metal of Group VI-B, and preferably also an organometallie of metal of Group I-A, IIA, II-B or III-A.

The lithiated polymers include, for example (a) the lithiated homopolymers of conjugated dienes containing 4 to 6 carbon atoms, including 1,3-butadiene, isoprene, piperylene, and 2,3-dimethyl butadiene; (b) lithiated copolymers of such dienes; and (c) lithiated copolymers of any one or more of these dienes with one or more vinyl monomers including styrene, methyl methacrylate, vinyl chloride, styrene derivatives such as alphamethylstyrene, and other recognized comonomers which on copolymerization with such a diene produce synthetic rubbers.

The salts of the transition metals are preferably chlorides, although other halides (bromides, iodides and fluorides) may be used as well as oxyhalides, sulfates, nitrates, acetonates, acetylacetonates, alkoxides, phosphates, etc. The metal is preferably tungsten although molybdenum and chromium salts may be used. The preferred compound is a halide, and particularly tungsten hexachloride or molybdenum pentachloride.

The organometallic is preferably a derivative of aluminum; however, an organometallic of another metal of Group I-A, II-A, II-B or III-A may be used.

The salts of the transition metals include, for example:

molybdenum pentachloride molybdenum pentafluoride molybdenum hexabromide molybdenum dichloride molybdenum oxytribromide molybdenum nitrate molybdenum acetylacetonate molybdenum sulfate molybdenum phosphate molybdenum pentaethoxide molybdenum perchlorite tungsten dichloride tungsten pentabromide tungsten hexafluoride tungsten oxytetrachloride 3,845,028 Patented Oct. 29, 1974 "ice tungsten-sulfate chromous chloride chromic chloride chromous nitrate chromic nitrate chromium oxychloride chromium orthophosphate chromous sulfate chromic-sulfate, etc.

The organometallic compounds which may be used include compounds which comprise alkyl groups of 1 to 10 carbon atoms, phenyl, naphthyl and methyl and ethyl derivatives of phenyl and naphthyl. Thus they include, for instance:

trimethylaluminum triethylaluminum tripropylaluminums tributylaluminums triamylaluminums trihexylaluminums triheptylaluminums trioctylaluminums trinonylaluminums tridecylaluminums triphenylaluminum trinaphthylaluminums tri-tolylaluminums trimethylnaphthylaluminums monoalkylaluminum dihalides dialkylalumiuum halides monoarylaluminum dihalides diarylaluminum halides and the corresponding alkyl derivatives of lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, barium, strontium, zinc, cadmium, gallium, indium and thallium. These include, for example:

methyl lithium ethyl sodium propyl potassiums butyl rubidiums amyl cesiums butyl-lithiums phenyl lithium naphthyl lithiums dimethyl magnesium diethyl calcium dipropyl bariums diamyl strontiums dihexyl zines dioctyl cadmiums trinonyl galliums tridecyl indiums trimethyl thallium methyl magnesium halides ethyl calcium halides propyl zinc halides butyl cadmium halides amyl gallium halides hexyl indium halides heptyl thallium halides octyl beryllium halides phenyl barium halides naphthyl-strontium halides The molar ratio of the amount of the organometallic compound to the salt of the transition metal used, may be varied from about 0.1 to 10, but usually substantially equal molar amounts of the two components will be used. About 0.01 to 10.0 moles of the combined weight of the two components will be used for each mole of live lithium inthe polymer being treated. Usually, about 2 moles (one mole of each component) will be found satisfactory.

The catalyst components may be added separately to the reaction mixture, or they may be previously mixed and allowed to stand and react with one another prior to addition to the reaction mixture.

The preferred catalyst is a combination of triisobutyl aluminum with tungsten hexachloride in hydrocarbon solvent.

The joining reaction is carried out in the reaction mixture in which the polymerization is carried out, without removal of the lithium from the polymer. Sodium polymers may be used.

The joining reaction results in a rubbery polymer having:

. Increased molecular weight.

. Broader molecular weight distribution.

. Decreased cold-flow properties.

. Increased Williams recovery.

. Substantial change in microstructure may occur.

The following examples are illustrative:

EXAMPLE 1 To a standard one-gallon reactor was added 3000 g. of a 17.6% butadiene-heptane solution (528 g. butadiene, 9.77 mole). Hexane or other hydrocarbon solvent may be used instead of heptane. Often heptane-hexane is used. The temperature of the solution was raised to 50 C. The polymerization of the butadiene was initiated by injecting 5.65 ml. of 1.12M (6.33 mmole) butyllithium in hexane with a syringe into the reactor through an injection port capped with a rubber septum. (This amount of butyllithium includes that necessary to kill impurities present as well as that used to initiate the polymerization.) The polymerization was allowed to proceed at 50 C. until the pressure was constant (4 hours). A sample of this cement was taken, the lithium was killed and the polymer was coagulated with methanol (Sample A).

After the reactor and contents had cooled to room temperature, 70 ml. of 0.102M WCl in benzene, (7.14 mmole) followed by 17.4 ml. of 0.409M triisobutylalu minum in heptane (7.12 mmole) was added to the vigorously stirred polymer solution. Samples (B-E) were taken periodically after the lapse of the times shown in the following table, by forcing the polymer out through an orifice in the bottom of the reactor with pressure. The samples were collected directly in methanol containing antioxidant.

Percent D SV (Dis-1,4 Trans-1,4 1, 2

No gel was formed. The stereo composition of the polymer remained substantially constant. The rise in DSV occurred within 5 minutes and no substantial rise occurred after that time, showing that the joining reaction was substantially completed within not more than 5 minutes. (The variation in the DSV of the joined polymers is of no consequence.)

We claim:

1. The process of increasing the molecular Weight of a polymer of the class consisting of terminally lithiated homopolymers of conjugated dienes containing 4 to 6 carbon atoms and terminally lithiated copolymers of such conjugated dienes and a vinyl monomer, which comprises joining the units of the polymer with substantially equimolar amounts of tungsten hexachloride and triisobutylaluminum which causes joining of the polymer and production of a polymer of increased molecular weight.

References Cited FOREIGN PATENTS 5/ 1965 Great Britain. 7/1966 France.

OTHER REFERENCES JOSEPH L. SCHOFER, Primary Examiner W. F. HAMROCK, Assistant Examiner US. Cl. X.R. 26094.7 HA

jgggy UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 'Patent No, 5,845,028 Dated OC'bObEI 29, 1974 Inventor) Tristram Walker Bethea and Adel Farhan Halasa It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column one, after line 6, the following should be added which was inadvertently left out:

--Assignee: The Firestone Tire & Rubber Company, Akron, Ohio Signed and sealed this 27th day of May 1975.

(SEAL) Attest:

' C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. THE PROCESS OF INCREASING THE MOLECULAR WEIGHT OF A POLYMER OF THE CLASS CONSISTING OF TERMINALLY LITHIATED HOMOPOLYMERS OF CONJUGATED DIENES CONTAINING 4 TO 6 CARBON ATOMS AND TERMINALLY LITHIATED COPOLYMERS OF SUCH CONJUGATED DIENES AND A VINYL MONOMER, WHICH COMPRISES JOINING THE UNITS OF THE POLYMER WITH SUBSTANTIALLY EQUIMOLAR AMOUNTS OF TUNGSTEN HEXACHLORIDE AND TRIISOBUTYLALUMINUM WHICH CAUSES JOINING THE POLYMER AND PRODUCTION OF A POLYMER OF INCREASED MOLECULAR WEIGHT. 